1. Field of the Invention
This invention relates to a polymeric cord structure for use in the reinforcement of articles such as pneumatic tires, hoses, belts, and other elastomeric articles. The cord has a core consisting of a single yarn or a plurality of continuous filament yarns laid side-by-side and a wrapper yarn wound helically around the core yarns.
2. Description of the Prior Art
Nylon and polyester tire cords are conventionally highly twisted structures consisting of two to five continuous filament, drawn, oriented yarns. The formation of these cords requires two twisting operations. The first operation is yarn twisting in which drawn, oriented yarn, containing only enough twist or tangle to hold the yarn together, is twisted on itself a desired number of turns per unit length of the yarn in either an S or Z direction. The second operation is cord twisting in which two or more of the twisted yarns prepared in the yarn twisting operation are twisted together. The direction of the twist in the cord twisting operation is opposite to that in the yarn twisting operation. Generally, the twist in the yarn and the twist in the cord have an equal number of turns, although more sophisticated twist relationships are possible. A typical nylon tire cord formed from two yarns each having a total nominal denier of 840 contains 12 turns per inch (tpi) of Z-twist in each of the two yarns and 12 tpi of S-twist in the cord. Such a cord is designated 840/2 (12.times.12). Other conventional nylon cords used in the construction of tires include 1260/2 (10.times.10) and 1890/2 (8.times.8). The yarn twisting and cord twisting operations are performed at slow yarn speeds (i.e. at about 15 to 20 yards per minute) and consequently add significantly to the cost of making tire cord (i.e. both operations add about twenty to forty cents per pound to the cost of the cord). It would be highly desirable to provide a less expensive tire cord.